1. Field of the Invention
The present invention relates to a polymer battery pack, and more particularly, the present invention relates to a polymer battery pack that can withstand a strong external impact and have a thin thickness.
2. Description of the Related Art
A related art polymer battery pack includes a lithium polymer battery, in which a protecting circuit is connected to a pouch type bare cell, and a case with a plastic frame that holds the lithium polymer battery. The pouch type bare cell receives an electrode assembly including a positive electrode plate/separator/negative electrode plate, and a polymer electrolyte in the interior of the pouch that consists of cast polypropylene(CPP)/aluminum/nylon (or polyethylene terephthalate(PET)). For reference, the polymer battery is named because it uses a polymer electrolyte, differently from a lithium-ion battery using a liquefied electrolyte.
On the other hand, the related art polymer battery pack can be easily damaged by an external shock such as bending, twisting and falling, etc. because the strength of the pouch and a plastic case surrounding it are weak. Therefore, it has problems that reduce stability and reliability.
In other words, the aluminum used for the pouch has a very thin foil shape, and the plastic case surrounding it is also very thin, so they can be easily deformed, broken and damaged by external force because of their weak strength.
Thus, the related art polymer battery pack is fabricated by after additionally attaching a reinforcing material made of stainless steel for reinforcing the strength of the pouch type bare cell connected to the protecting circuit, covering the pouch type bare cell with the plastic case, and then attaching label paper around the pouch type bare cell combined with the plastic case.
However, the reinforcing material made of stainless steel for reinforcing the strength of the related art polymer battery pack usually has a definite thickness of more than 0.1 mm and a definite weight. Therefore, it is difficult to make a thin polymer battery pack and reduce the weight of the polymer battery pack according to the trend of slimming and miniaturization of the battery pack.
Also, the related art polymer battery pack additionally includes the reinforcing material made of stainless steel. Therefore, it has problems to increase a manufacturing cost and the number of manufacturing processes due to the addition of the reinforcing material.